Using a mutation observer to watch for added child nodes

MutationObserver-childList.js

(function() {

  // Select the node to observe
  var targetNode = document.querySelector('#sqs-cart-root');

  // If the targetNode exists on our page
  if(targetNode){
  
    // Watch when nodes are added to targetNode, or its descendants
    var config = {
      childList: true,
      subtree: true
    };

    // When mutation is observed
    var callback = function(mutationsList) {

      var cartTitle = document.querySelector('.cart-title')
      var continueShopping = '<br><a href="/all-courses" style="font-size: .5em;" id="continue-shopping">Continue Shopping</a>';

      for(var mutation of mutationsList) {
        // If we have a cart-title, but don't have our continue-shopping link yet, add it
        if(cartTitle && !document.querySelector('#continue-shopping')){
          cartTitle.innerHTML = cartTitle.innerHTML + continueShopping;
        }else{
          // Stop observing, we did what we needed
          observer.disconnect();
        }
      }
    };

    // Create a new observer
    var observer = new MutationObserver(callback);

    // Start observing
    observer.observe(targetNode, config);
    
  }
  
})();